U.S. Pat. No. 2,031,684 to Berger discloses a tile spacer comprising a preferably cross-shaped element, but requires that the spacers have an axial thickness substantially less than the thickness of the tiles (col. 2, lines 21-25).
U.S. Pat. No. 4,571,910 to Cosentino discloses an apparatus for laying tiles in which a plurality of grooves running perpendicularly from the edges of the tiles are formed in the rear surfaces of the tiles, and a plurality of elongated spacer elements is provided in the grooves.
U.S. Pat. No. 4,503,654 to Cosentino discloses a method and apparatus for constructing a surface from a plurality of similar polygonal tiles in which spacer members having a flat base and a rectangular flange bisecting the base are securely affixed to the rear face of the tile.
U.S. Pat. No. 4,953,341 to Joos discloses a spacer element for insertion between spaces between tiles for uniform spacing of the tiles, comprising a plurality of legs extending radially from a common juncture with the legs being formed with beveled edges to facilitate removal after an adhesive has cured.
U.S. Pat. No. 3,512,324 to Reed discloses a portable floor adapter for use over a permanent floor or over a floor covered with a rug or carpet made of several sections adapted to abut in a predetermined pattern, the sections being provided with magnets and magnetic apertures for holding the sections assembled.
U.S. Pat. No. 3,438,161 to Koch discloses a wall construction employing core positioners for spacing the core away from the walls of the forms.
U.S. Pat. No. 2,257,001 to Davis discloses a building unit and construction employing various types of joining units for slabs made of gypsum or the like.
U.S. Pat. No. 2,015,813 to Nielsen discloses the use of dowel pins and bores for joining wood block flooring.
U.S. Pat. No. 2,008,244 to Crooks discloses a self-leveling floor in which a V-shaped groove is formed along an edge of a block and a V-shaped tongue is formed on another edge with the apex of the tongue being rounded.
U.S. Pat. No. 4,680,914 to Migliore discloses a method of installing marble panels on a flat wall in which a slab or marble is cut into a plurality of thin marble sheets that are then attached to a backing panel.
U.S. Pat. No. 4,840,825 to Aristodimou discloses a tile for flooring or wall cladding with a thin stone layer bonded to a substrate made of three sublayers and with the sublayers displaced to define tongues and grooves.